Scavenging reversible internalcombustion engine



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SCAVENGING REVERSIBLE INTERNAL'COMBUSTION ENGINE Filed Junef` 14,- 19435 sheetfsfsheet 2 Gttomegs Feb. 5, 1946. K, FRQEHUQH 2,394,237'

SCAVNGING REVERSIBLE INTERNAL-COMBUSTIQN ENGINE Fned June 14, 1943 5-sheets-snee; s

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SCAVENGING REVERSIBLE INTERNAL-COMBUSTION ENGINE Filed June 14, 3.943 5Sheets-Sheet 4 I v Ho :inventor 'Kuri Frgehlinch CutorneL-gs Feb. 5,1946; K, F'RQ'EHLICH 2,394,237

SCAVENGING REVERSIBLE INTEBNAL-CMBUSTION ENGINE Filed June 14, 1945 5Sheets-Sheet 5 IIS Kuri Froehlirch ,@1095 CttornegS Patented F eb. 5,1946 scAvnNeING REVERSIBLE INTERNAL.- eoMu-srloN ENGINE Kurt Froehlich,Milwaukee, `Wis.,l assgnor .to Nordberg Manufacturing Company,rMilwaukee Wis., a corporation of Wisconsin Application .lune 14, 1943Serial No.. 49.0.8037

I Claims. (Cl. 12S-41) This. invention relates to the scavenging ofreversible internal combustion engines, and particularly to. automatic4means for rendering an engine-driven scavenging blower indifferent tothe direction of rotation of the engine.

Where scavenging air is furnished by an engine-driven positivedisplacement rotary blower, such. as a Roots type blower, or by anyother blower or pump not inherently indifferent to its direction ofrotation, it is necessary either to reversev the blower drive when theengine is reversed, or to interchange the inlet and dischargeconnections, of the blower as an incident tof lreversal of the engine.

In the prior art the mechanism which reverses the action of the blowerisA mechanically`V actuated-t frorn the reversing gear. This arrangementworks very nicely ifl thev engine is allowed to stop before thereversing gear is` put into reverse posi-- tion, but to stop the enginequickly it is the practice --to plug the engine by moving thereversegear into reverse starting positionwhile the engine continues itsmotion. This causes thev blowerV to evacuatethe scavenging manifold,which is objectionable.

The present invention provides a valve which is: notA operated directlyby the reversing gear but which responds to partial evacuation of ascavenging manifold to cause reversing. Thus in reversing, whether theengine is plugged or is allowed to stop before being set in reverse,response of the blower reversing device will not occur until the enginehas actually startedto turn reversely. Consequently the objectionableaction of the prior art devices is avoided.

As illustrated in the accompanying drawings the valve will reverseautomatically as soon as the engine crank shaft has turned reverselythrough a moderate angle, and will thereafter maintain its positionuntil another reversal direction has occurred. No. actuating connectionbetween the valve and the engine reversing gear is required.

The valve is so arranged that developmentl of a positivepressure in themanifold tends tomaintain the unbalanced reversing valve in position.,whereas depression of manifold pressure below atmospheric establishes areversing tendency- This tendency cannot` persist through the entirereversing motion. Hence use is made of some means, conveniently animpositivo detent, which n1 this. way, start or une. shift is delayeduntil manifold pressure is; reduced substantially. Thereupon the.differential pressure becomes effective. for a substantial angle ofmotion, .so that the valve acquires: sufficient. momentum to.. cause. itto move full stroke, once it starts. In this Way the valve can be causedto reverse automatically when the crank shaft has turned reverselythrough a moderate. angle. Such motion can be caused to: occur, uponreverse rotation of the; crank shaft. through less than 60 degrees.

Two embodiments of the. invention willv be described, each of whichoffers a. favorable location of the blower and. valve, and each of whichhas the advantages of favorable flow paths for the. air in both settingsof the valve, and of simple i driving trains from the engine crankVshaft to resists initial motion'. away from each. limiting the blower.

As a secondary feature an interlock is provided between. the unbalancedreversing valve and the control lever which is shiftable from a stop.position in opposite directions through reverse starting ranges andthen through fuel ranges.L A gear of this general' type is shown in thepatent to Ramstad. 2,243,883',4 June 3 1941, and another' in thepatentto Froehlich and. Grieshaber 2,304,161', December 81942. Thefunction ofthe interlock is to allow the controller to move from sayforward. position through the. stop position and into the reversestartingy position. Without. interference but, to. prevent. motion into.the reverse fuel range until the unbalanced` reversing valve which con,-trols. the.- blower has shifted to reversey position. This. interlock iseffective. both types of reversal so. that it. -is impossiblel tooperate the engine under fuel until the. blower is functioning properly.

In the. drawings.:

Figure l is an elevation of an engine equipped with the. invention andshowing the location. of the blower and valve relatively to thecylinders and: the scavenging. manifold. The drive train to4 ther bloweris indicated. in dotted lines. In this View the protective interlock forthe engine. con,- troller is. shown.

Fig. 2 is a section through. the, blower, valve and; manifold on theline` 2-2 of Fig. 3.

Fig. 3 is a. section on the line 3 3. of Fig.. 2.

Fig.. 4 isa horizontal section. through the blower housing on the line4.-4 of Fig.. 5..

Fig.. 55 isv an elevation. .of thel blower housing showing the portedfacev with which the; rotary valve.l coacts. and uponwh-ich the: valve`housing is mounted.. i

Fig. 6. is--a section` on theline. 6--6 .ofFig.. 5.

Fig. '1 is a plan view of a modified embodiment in which the blower axesare parallel with the crank shaft and the valve is mounted above theblower.

Fig. 8 is a vertical axial section. through the valve and blower of Fig.'1.

Fig. 9 is a section on the line-9 9 of Fig. 8.

Fig. 10 is a section on the line lll-I0 of Fig. 8.

The engines selected for illustration are of the two cycle portscavenged type with check valves (sometimes called Fiat valves) arrangedto prevent flow from the cylinders through the scavenging ports to thescavenging manifold. Such valves are a familiar and desirable`componentof two cycle port scavenged engines and are important in connection withthe invention because they make it possible to reduce manifold pressurebelow atmospheric pressure. Some such means is essential to operation.of the device but means other than Fiat valves could be used.

. In applying the invention to four cycle engines or any engine not ofthe port scavenged type with check valvesV in the scavenging path, somemeans must be supplied to prevent back ow from the atmosphere such asmight occur through any open scavenging port or valve to the manifold.

In the present disclosure the Fiat valves typify any such means.

Simply as bearing on general proportions of parts in the drawinga'and onstatements of direction it may be stated that the engines selected forillustration have nine vertical cylinders in line.

First embodiment The embodiment shown in Figures 1 to 6 will Vlirst bedescribed. Figure 1 indicates the rela- 18, A connection I9 leads fromhousing I1 to manifold I3. The valve housing is thus nearly in linewiththe manifold.

, The crank shaft 20 carries a bevel gear 2I which drives a pinion 22 onthe lower end of blower drive shaft 23 which is sustained by the pendantbearing housing 24.

The two impellers 25, 26 shown in Fig. 2 are driven by shaft 23,impeller 25 being driven directly and impeller 26 by the gears 21, 28shown in Fig. 1. Since the Roots type blower here shown is well knownand involves no patentable novelty it is deemed unnecessary to go intofurther detail. Additional details of blower construction are shown inFig. 8 to which reference can be made if desired.

Within the manifold I3 are the Fiat valves. There are two valve unitsper cylinder. Each unit comprises a bonnet 29 whose interior is incommunication with the scavenging ports in the cylinder walls, an upperstack of check valves 3 I, and a similar lower stack of check valves 32.Each stack comprises a set of superposed annular 'slotted seats eachcontrolled by an annular plate valve. The valves are light, the valvelift is small and the port areas are large in the aggregate.

Thus the Fiat valves open rapidly, offer little re' sistance to flowfrom the manifold to the cylinder and close instantly against reverseflow. VThey are in extensive use in port scavenged engines.

The impellers 25, 26 of the blower turn in the usual oval chamber 33within housing I6 and mesh with each other. The chamber 33 has a largeport 34 which leads to the encircling passages 35, and at the oppositeside a port 36 which leads to the downward extending passage 31. Figs.4, 5 and 6 will make the arrangement clear. At the side t0- ward theobservervin Fig. 1 the housing IE has a plate-bke wall 38, to which thehousing i1 of the reversing valve is attached. In the wall 38 are twodiametrically opposed sector shaped ports 39 and 4I. Port 39 is indirect communication with both the passages 35 and port 4l with passage31. The ports 39 and 4l are the terminal connections of the blower whichmust be interchangeably connected with manifold I3.

Formed in the cylindrical wall of housing I1 are two opposed rectangularports 42 and |13 which are displaced 90 from ports 39 and 4l. Port 42leads to connection I9 and hence to manifold I3, and port 43 vleads frominlet air connection d4. The

inlet connection may lead from the engine room or may be piped to anysuitable air inlet.

Turning on trunnions which are journaled in bearings 45 in plate 38 andin cover I8 is an unbalanced reversing valve having blades 46 and 41 ofunequal lengths. The blade 46 is the longer, and to compensate, maskingseats 48, 45 are provided to coact with lthe shorter blade' 41.

The limiting positions of the valve are determined by stops 5I, 52 whichare engaged by blade 46. These are so placed that the blade 4B mustswing through a substantial angle away from each stop before the bladeovertravels the proximate edge of port 42. When it does so, blade 41will clear masking seat 48 or 49 as the case may be. During this rangeof motion the blower connections are not affected, but the valveacquires momentum Vsufficient to shift it full stroke.

-Within this range of motion the valve is pressure-biased toward theadjacent stop 5I or 52 if pressure in manifold I3 is above atmosphericand away therefrom if it is below atmospheric. Depression of manifoldpressure caused by initial reverse motion of the blower causes the valveto shift.

To delay shift of the valve until manifold pressure has beensufliciently reduced to cause full stroke-motion of the valve, animpositive detent, effective at each limit ofmotion is provided.

, This comprises an arcuate cam 53 keyed to one of the trunnions onwhich the valve turns. A

. spring urged plunger 54 forces a roller 55 against The cam is soproportioned as to serve as a.

counterbalance so that the valve has no gravity bias. This is desirableparticularly where the valve turns on a horizontal axis. It is desirableeven if the valve be mounted on a vertical axis where the engine is usedon locomotives or ships.

In Figure l, 56 represents the control stand and 51 is the maneuveringlever. Sofar as is here material, the lever 51 has a midposition markedstop in which the starting mechanism which turns the engine over isinert. This starting mechanism might be of any type but in large Dieselengines commonly involves a distributing valve gear which admitscompressed air to the various cylinders in timed relation to theposition of the crank shaft;

Simply as an example of such connection it mounted above the blower.

may be stated that the lever 51 `'might heappr'opriately linked to thearm 04 shown in Figure 2 fof the Ramstad patent abovefid'entied or V.totheV arm 14 shown on Figure 2 of -th'e .Froehlich and Grieshaber patentabove identified. '-Ih'es'e patents show examples of reversing gears 1inwhich a maneuvering lever such as the lever 51 is movable from a neutralposition in opposite directions, first through a starting range and thenthrough a fuel range. These two examples are of the air starting type,but the particular mechanism used to start the engine rotating is notmaterial to the present invention.

Tf the lever 51 is moved into the vahead o1' astern starting range, theengine is turned over ahead or astern as Vthe case may be. If the lever51 4is moved` beyond the starting range into the fuel range 'eitherahead or astern, the starting mechanism is rendered inactive and fuel issupplied to the engine at rates which increase with ythe displacement ofthe lever 51. The function lof ythe interlock to be ldescribed is toprevent motion from either starting range into the corresponding fuelrange until the blower reversing valve 45, 41has shifted appropriately.

In Figure 1 this valve is shown in its forward position and lever 51 isshown arrested at the limit 'of the ast-ern starting range asit would beVset to plug the engine. It is there arrested by an interlock lever 53.This has an upper hook 59 which prevents entry into the astern fuelrange and a lower hook 6| which when propverly "positioned, preventsentry of lever 51 into the forward fuel range.

y In Figure l the hook 55 is shown engaging the lug 52 mounted on lever51. If the lever 58 is turned coun'ter-clockwise, hook 59 is retractedfrom the path of the lug 62 and hook 6| is projected into said path butin a position which will prevent entry of lever 51 into the forward fuelrange. The lever S shifts between the positions justmentioned inresponse to the shifting of the rotary valve 46, 41. The actuatingconnections are diagrammed as a link 63, bell crank 54, link 65, bellcrank @E and link 61. is connected to a crank pin 58 mounted on the camdisk 53. rIlhus the shift of the valve interchanges the hooks 59 and 6|making them functionally effective selectively.

,'-No part of the control mechanism is illustrated other than `theinterlock, Vand the connections between the rotary valve and the.interlock member 'are indicated in simple diagrammatic form and may bevariously embodied.

Second embodiment The second embodiment illustrated in Figures 7 to 10is functionally identical with the first embodiment. The parts arediderently arranged. To avoid repetitious description parts in thesecond embodiment corresponding to parts in the first are 'given thesame numerals increased by mi), so that they can be readily identified.

The basic diiferences are that the blower is mounted with the axes ofits impellers parallel with the vcrank shaft and the reversing valve isThe axis of the unbalanced reversing valve is vertical instead ofhorizontal. This arrangement entails some differences of detail whichwill be briefly explained.

Instead of the ibevel gear 2| va spur gear |2| is |34 and |35 Aat'opposite sides of the oval blower chamber |33 communicate respectivelywith pasf- 'Ihis last sages '|35 and |31 which extend upward at op:

posite sides of the housing H6.

The circular housing H1 which encloses' the reversing valve has fourperipheral ports. Thus the ports |39 and '|41 Vare opposed to each otherand have V-'shaped extensions in plate |38. The ports |42 and |43 areopposed 'to each other. This arrangement 'gives larger port areas andfreer now than is had in the firstembodiment.

With the valve inthe position of Figure l0 the inlet 'connection I 44 isconnected by way of ports |43 'and |4| `with the Vport |3`6in the blowerhousing. Similarly the port |54 in the blower housing 'connected by way,of the ports |39 and |42 to passage ||9 and thus to the scavengingmanifold H3.

'Ihe impositive detent mechanism is essentially the same as that'already described. The valve wings have a substantial angle of idlemotion before they' overrun the margins of the ports |42 and |43.

In Figure 7 the point of connection `|58 for the interlock mechanism isindicated. No other parts of the interlock mechanism are illustratedsince they would Iconfor-m basically with what is fully illustrated inFigure 1.

Operation A Suppose, for example, that the engine is operating forwardand that the valve 45, 41 is in the position indicated in Vdottedlinesin Figure l. During forward operation the maneuvering lever 51 would besome where in the ahead fuel range. 'Ihe engineer desires to stop andreverse the engine. He may move the handle 51 to stop position and waituntil the engine stops, or he may move the handle to the positionillustrated in tion, the valve 46, 41 will automatically shift to asternposition and by its shift will retract the hook 59 and protrude the hook'61. Thereupon the operator may move the maneuvering lever into theastern fuel range. The protrusion of the hook 6| establishes a Vsimilarsafeguard forthe next reversal, so that during such reversal theoperator may move the handle 51 through the starting range but notbeyond that range until the blower connections have been reversed.

The automatic shift of the valve 45, 41 will now be described in detail.

In the case of either embodiment, if the engine is stopped and then putin motion in the reverse direction, the blower will first operate 60 todraw 'air from the scavenging manifold. The

Fiat valves will prevent the entrance of air through any open scavengingport and consequently the pressiue in the scavenging manifold.

will be reduced.

The action of the detent is such that when pressure in the manifold hasbeen reduced moderately the unbalanced valve will overpower the detentand start to move. Through the first few degrees of motion the portconnections are 0 not changed. Suiiicient momentum will be `gatheredthrough this range of `motion to cause the valve to swing full stroke.As it approaches the opposite limit of motion, the development vof.positive pressure in the scavenging manifold 'by the continuedloperati'o'r-i of the blower will force the there.

Consequently, the reversing valve operates automatically as an incidentto reversal but requires no mechanical connection with the reversinggear. Because it is in static balance (the detent arm serving as acounterweight) the valve is indifferent to gravity effects, and to anymotion which it may encounter when used on a ship or locomotive. Y

An examination of the drawings will indicate that the blower andvalve-are located in line with the cylinders and that the iiow pathsfrom the .blower through the valve to the scavenging manifold and fromthe air intake to the blower are simple, direct and of adequate crosssectional area. Y 'Y While two embodiments of the invention have beendescribed in considerable detail, they are intended to illustrate theprinciple of the invention without implying any necessary limitation tothe specific structure so described.

What is claimed is:

. l. The combintion of a reversing internal combustion engine having ascavenging manifold; a

-blower driven by the engine and acting to propel air in oppositedirections between the terminal connections of the blower according asthe engine operates in one or the other direction; and means responsiveto a pressure differential between said manifold and blower,rabnormal indirection, and created by operation of the blower, to interchange saidterminal connections as to communication with said scavenging manifold.

2. The combination of a reversing internal combustion engine having ascavenging manifold; a blower driven by the engine and acting to propelair in opposite directions between the terminal connections of theblower according as the engine operates in' one or the other direction;and an unbalanced valve having two positions in which respectively itinterchanges said terminal connections as to communication with themanifold and with an air supply, said unbalanced valve being arranged toshift in response to a pressure differential between said manifold andblower, abnormal in direction, acting on the valve anddeveloped byoperation of the blower.

3. The combination of a reversing internal combustion engine having ascavenging manifold; means for preventing back flow through themanifold; a blower driven by the engine and acting to propel air inopposite directions between the terminal connections of the bloweraccording as the engine turns in one or the other direction; valve meansshiftable between two limiting positions in which respectively itinterchanges said terminal connections, connecting a selected one withthe manifold and the other with the atmosphere; and means effective ineach limiting position of the valve, and responsive to Aa definitereduction of manifold pressure below atmospheric pressure, to impart areversing impulse to the valve.

4. The combination of a reversing internal combustlon engine having ascavenging manifold; means for preventing back ow through the manifold;a blower driven by the engine and acting to propel air in oppositedirections between the terminal connections of the blower according asthe engine turns in one or the other direction; valve means shiftablebetween two limiting positions in which respectively it interchangessaid terminal connections, connecting a selected one valve, to its otherlimitof motion and 'retainit with the manifold and the other with theatmosphere; and pressure Voperated means effective through a limitedrange of valve motion measured from each limiting position, andresponsive to a definite reduction of manifold pressure belowatmospheric pressure to impart reversing momentum to the valve.

5. The combination of a reversing internal combustion engine having ascavenging manifold; means for preventing back flow from the engine tothe manifold; a blower driven by the engine and acting to propel air inopposite directions between the terminal ow connections of the bloweraccording as the engine runs in one or the other direction; anunbalanced multi-way valve shiftable between two limiting positions inwhich respectively it interchanges said terminal connections, connectinga selected one with the manifold Vand the other with atmosphere, saidvalve being pressure-biased toward or away from each limiting positionwhen near the same according as manifold pressure is above or belowatmospheric pressure, said valve having near each of said positions arange of idle motion in which it does not affect the communicationscontrolled by it; and impositive means serving to retain said valve ineach limiting position.

6. The combination of a reversing internal combustion engine having ascavenging manifold; means for preventing back flow from the engine tothe manifold; a blower driven by the engine and acting to propel air inopposite directions between the terminal flow connections of the bloweraccording as the engine runs in one or the other direction; anunbalanced rotary blade valve shiftable between two limiting positionsin which respectively it interchanges said terminal connection,connecting a selected one with the manifold and the other withatmosphere, the unbalanced character of said valve serving to bias saidvalve toward or away from respective limiting positions when near thesame according as manifold pressure is then above or below atmosphericpressure; masking means coacting with the blades of said valve to afforda range of idle motion near each limiting position; and impositive meansserving to exert a retaining tendency on the valve in each limitingposition. L

7. The combination of a reversing engine having a crank shaft, aplurality of cylinders in line, and` a scavenging manifold extendingalong said line of cylinders; a rotary blower mounted in line with saidcylinders and connected to be driven by said crank shaft, said blowerbeing of a type which propels air in opposite directions betweenterminal connections according as it is driven in one or the otherdirection; a reversing valve device mounted as a unit with said blowercontrolling the terminal connections thereof and having an air intakeport and a port leading to the end of said manifold, said valve deviceincluding a flow directing member shiftable between two positions tointerchange said ports as to communcation with the terminal connectionsof the blower; and means responsive to manifold pressure and serving toretain said iiow directing member in either of said positions ifmanifold pressure be then above atmospheric pressure, and to propel saidvalve toward the other ofr said positions if, manifold pressure bereduced below atmospheric pressure.

8. The combination defined in claim 7 in which the valve device ismounted on the side of the blower and approximately in line with the endof the manifold. Y

9. The combination of a reversing engine having a crank shaft, aplurality of cylinders in line, and a scavenging manifold extendingalong said line of cylinders; a rotary blower mounted in line with saidcylinders and connected to be driven by said crank shaft, said blowerbeing of a type which propels air in opposite directions betweenterminal connections according as it is driven in one or the otherdirection; a reversing valve device mounted on the blower substantiallyin line with said manifold, said device controlling said terminalconnections and including a housing having an air intake port and a portleading to the end of said manifold, and a flow directing membershiftable between two positions to interchange said ports as tocommunication with the terminal connections of the blower; and means forshifting said now directing member between said positions as an incidentto reversal of the direction of rotation of the engine.

10. The combination of a reversible internal combustion engine having ascavenging manifold; means for preventing back flow from the engine tothe manifold; a blower driven by the engine and acting to propel air inopposite directions between the terminal connections of the bloweraccording as the engine runs in one or the other direction; valve meansshiftable between two limiting positions in which respectively itinterchanges said terminal connections, connecting a selected one withthe manifold and the other with the atmosphere; actuating meansassociated with the valve means, responsive to the pressure differentialbetween the manifold and atmosphere and effective when the valve meansare near either limiting position to urge the valve means toward suchposition if manifold pressure predominates and away therefrom ifatmospheric pressure predominates, there being a range of idle motionnear each of said limiting positions, in which the actuating means moveswhile the blower connections are not affected by the valve means; andimpositive means serving in said limiting positions to resist motion ofthe actuating means therefrom until a substantial pressure differentialhas been established.

11. The combination of a reversing internal combustion engine havingcylinders, a scavenging manifold and scavenging ports leading therefromto the cylinders; check valve means permitting iiow from the manifoldthrough said ports to the cylinders but inhibiting reverse flow; ablower driven by the engine and acting to propel air in oppositedirections between the terminal connections of the blower according asthe engine runs in one or the other direction; valve means shiftablebetween two limiting positions in which respectively it interchangessaid terminal connections, connecting a selected one with the manifoldand the other with the atmosphere; actuating means associated with thevalve means, responsive to the pressure differential between themanifold and atmosphere and effective when the valve means are neareither limiting position to urge the valve means toward such position ifmanifold pressure predominates and away therefrom if atmosphericpressure predominates, there being a range of idle motion near each ofsaid limiting positions, in which the actuating means moves while theblower connections are not affected by the valve means; and impositivemeans serving in said limiting positions to resist motion of theactuating means therefrom until a substantial pressure differential hasbeen established.

l2. The combination of a reversing internal combustion engine having ascavenging manifold; a controller for said engine shiftable through amid-position in which the engine is stopped and through starting rangeson each side of said stop position in which the engine is caused to turnin opposite directions, said controller being shiftable to fuel rangesbeyond said starting ranges in which fuel is supplied to the engine forforward and reverse running respectively; a scavenging blower driven bythe engine and acting to propel air in opposite directions between theterminal connections of the blower according as the engine operates inone or the other directions; means responsive to a pressuredifferential, abnormal in direction, and created by operation of theblower to interchange said terminal connections as to communication withsaid scavenging manifold; and an interlock device connected with thelast named means and serving to prevent the controller from beingreversed beyond the starting range until an appropriate interchange hasoccurred.

13. The combination of a reversing internal combustion engine having ascavenging manifold; a controller for said engine shiftable through amid-position in which the engine is stopped and through starting rangeson each side of said stop position in which the engine is caused to turnin opposite directions, said controller being shiftable to fuel rangesbeyond said starting ranges in which fuel is supplied to the engine forforward and reverse running respectively, a scavenging blower driven bythe engine and acting to propel air in opposite directions between theterminal connections of the blower according as the engine operates inone or the other direction; an unbalanced valve having two positions inwhich respectively it interchanges said terminal connections as tocommunication with the manifold and with an air supply, said unbalancedvalve being arranged to shift in response to a pressure differential,abnormal in direction, acting on the valve and developed by operation ofthe blower; and an interlock device connected with said unbalanced valveand serving to prevent the'controller from being reversed beyond thestarting range until the unbalanced valve has shifted.

14. The combination of a reversible internal combustion engine having ascavenging manifold; a controller operable to start said engine ineither direction by motion through starting ranges, said controllerbeing movable beyond said starting ranges into fuel ranges in which fuelis supplied to operate the engine; a scavenging blower of the type invwhich flow reverses upon reversal of the direction of rotation, saidblower being driven by the engine; interchange means operable by theinitial rotation of the engine in either direction to cause said blowerto deliverair to said manifold; and an interlock actuated by saidinterchange means and inhibiting reversal of said controller beyond saidstarting range until said interchange means have functioned.

15. The combination of a reversible internal combustion engine having ascavenging manifold; a scavenging blower of the type in which owreverses upon reversal of the direction of rotation, said blower beingdriven by the engine; and interchange means responsive to reduction ofmanifold pressure, and operable by the initial rotation of the blower ineither direction to cause said blower to deliver air to said manifold.

KURT FROEHLICH.

